Known processes for producing an oxime are as follows.
(i) A process where in the presence of a N-hydroxyimide compound and a compound produced by introducing a protecting group (for example, an acyl group such as an acetyl group) into a hydroxyl group in the N-hydroxyimide compound, a compound having a methyl or methylene group is reacted with a nitrous acid ester or nitrite (Patent Reference No. 1). Here, the N-hydroxyimide compound is derived from an aliphatic polyvalent carboxylic anhydride (cyclic anhydride) such as N-hydroxysuccinimide or an aromatic polyvalent carboxylic anhydride (cyclic anhydride).
(ii) A process where a cycloalkane or the like is photo-nitrosated (Patent Reference No. 2).
(iii) A process where in the presence of a catalyst such as titanosilicate, a ketone, ammonia and hydrogen peroxide are reacted (Patent Reference No. 3).
(iv) A process where a corresponding ketone is condensed with a hydroxylamine produced by metathesis of a hydroxylamine sulfate mineral acid salt.
Among these, the process (iv) is versatile and common. For example, cyclododecanone oxime as a starting material for laurolactam is produced by reacting cyclododecanone with a hydroxylamine mineral acid salt (Patent Reference No. 4).
According to the process (iv), in the production of an oxime, the use of hydrophobic solvent is advantageous in the light of an easier oil/aqueous separation and solvent recovery, and desirable in the light of an influence of water on subsequent Beckmann rearrangement of the oxime can be reduced (Patent Reference No. 5). However, when an oxime is produced from a ketone and hydroxylamine in a biphasic system of a hydrophobic solvent and water, the reaction takes a long time. In particular, when a ketone which is less easily distributed into an aqueous phase is used in oxime-forming, the reaction tends to take a longer time. This leads to need a larger apparatus and thus enormous equipment expenses, which is disadvantageous in the light of productivity and economy.